Simply Entity Equipment

Simply Entity Equipment (SEE) allows mobs to spawn with armour and weapons, and has built-in support for Simply Swords and Simply Bows (though it does not depend on these mods).

By default, the mod comes packaged with a set of default values – so you can throw it into your modpack and it will just work.

If you would like to customise the gear that mobs can spawn with, you can do so by using the fully data driven system built into the mod. Read more on the github: https://github.com/Sweenus/SimplyEntityEquipment